Companion Planting

This is a technique favoured by organic gardeners for prevention of Pests and diseases.

The theory behind companion planting is that plants have specific likes and dislikes concerning their close companions in the garden and will do better if planted in close proximity to the correct plant. Many of the recommendations for companion planting are based on folklore and, as with many of these tales, contain some truth.

There is a well-known theory that carrot fly are attracted by the smell of carrots, so, if the carrots are planted in-between rows of onions, the onions will mask the smell of the carrots, so preventing attack by carrot fly. Another theory is that the Cabbage white butterfly is attracted by the smell of Cabbages. If the highly aromatic plant Tagetes is planted in-between the rows of Cabbage, the butterfly will be attracted to the Tagetes instead.

French Marigolds have been tested by planting in amongst Potatoes that were infected with eelworm. It was found that the eelworm population was drastically reduced. In scientific tests it was found that this was indeed true. The Marigold has a secretion that comes from the roots, which affected the eelworms. French Marigolds are also said to kill weeds, in particular Couchgrass but this has not yet been proved.

Tagetes and Calendula planted near to Roses will greatly reduce the attacks of aphids. This is because these plants attract hoverflies, which lay eggs, and the larvae in turn, eat aphids. It is a bit more difficult to attract some of the other predatory insects. Some such as Ladybirds, Lacewings and several species of wasps that that feed on and lay their eggs in aphids, can be attracted by planting as varied a collection of plants as possible.

Over the years there have been a number of suggested plant combinations that work together in fending off insect pest problems and promote plant growth and lure beneficial insects (predators of pests). Much of the information relates to the experience and suggestions from gardeners. These are good companions, whereas plants that hinder growth of another plant are antagonistic.

The list below is not definitive. It has been collated from a lot of different sources such as old gardener's tales, myths, beliefs and a few known facts. I suggest that you try some of them, IF they work - great, IF they don't, then you haven't lost anything and perhaps you will have gained a little more experience in growing something else that you might not normally grow.

Vegetable and Plant Companions

Vegetable/Flower	Beneficial to	Antagonistic to
Alyssum	Re-seeds frequently, gradually breaks up & adds to the organic level of the soil *Esp. white alyssum	...
Asparagus	Parsley, tomato, basil	Onions, potato
Aubergine	Beans, potato, pea, tarragon, thyme	...
Basil	Bean, Cabbage, tomato Most plants	Rue
Beans	Beet, borage, Cabbage, carrot, cauliflower, cucumber, corn, marigold, squash, strawberry, tomato *Nitrogen-fixing	Chives, fennel, garlic leek
Beet	Cabbage, kohlrabi, dwarf beans, onions, Runner Beans	...
Borage	Strawberry, Tomato.	...
Broad Beans	Potato, lettuce	Fennel
Broccoli	Bean, celery, chamomile, dill, mint, nasturtium, onion, potato, sage, rosemary	Lettuce, strawberry, tomato
Brussels Sprout	Bean, celery, dill, hyssop, mint nasturtium, potato, sage, thyme	Rosemary, strawberry
Cabbage	Bean, beet, chamomile, dill, hyssop, mint, nasturtium, onion, potato, sage, rosemary.	Grape, strawberry, tomato, thyme.
Caraway	Peas	...
Carrot	Bean, chives, leek, onion, pea, lettuce sage, Scorzonera, tomato, *Deters onion flies	Dill, rosemary, radish
Catnip	...	Ants, Aphids, Flea beetles, Weevils
Cauliflower	Bean, beet, celery, chamomile, dill, hyssop, mint, onion oregano, sage, radish	Potato
Celeriac	Bean, Cabbage, leek, onion, tomato	...
Celery	Bean, Cabbage, leek, onion, tomato	Parsnip, potato
Chamomile	Cucumber, mint, radish, roses	...
Chervil	Carrot, radish	...
Chives	Cures blackspot on roses, inhibits growth of apple scab	Discourages insects from climbing fruit trees,
Clover	...	Deters Cabbage root flies
Cucumber	Bean, broccoli, carrots, celery, Chinese Cabbage, lettuce, pea, radish, tomato	Rue, sage
Dead nettle	Good companion for fruit trees;	Deters potato bud
Dill	...	Repels aphids and spider mites
Elderberry	...	General insect repellent
Eucalyptus	...	General insect repellent
Fennel	...	Deters aphids
Garlic	Good companion for fruit trees	General insect repellent, deters, aphids
Horseradish	Potato, Good companion for fruit trees (very invasive)	...
Hyssop	Good companion for grapes;	Repels Cabbage-white butterfly, flea beetles, insect larvae
Kohlrabi	Beet, onion	Bean, cucumber, pepper, tomato
Leeks	Carrots, celeriac, celery	Broad bean, broccoli
Lettuce	Beet, Cabbage, carrots clover, pea, radish, strawberry	Beet, beans, parsley, parsnip
Lupins	Good companion for roses *Nitrogen fixer	...
Marigolds (Calendula)	...	Deters asparagus, beets.
Marigolds (Tagetes)	Attract hoverflies (aphid predators), Good companion for roses	Reduce the number of nematodes in soil, Reduces Cabbage pests.
Melon	Corn, peanut, sunflower	...
Milkweed	...	Deters aphids
Mustard	...	Reduces aphids
Nasturtium	Gives off ethylene gas that helps in early ripening of fruit (though too many may inhibit growth) Keep away from broccoli, Brussels sprouts, potato, radish, squash.	Reduces aphids, Cabbage worms, deters woolly aphids and whiteflies. Prone to blackfly
Onion	Beet, Cabbage, carrot, chamomile, corn, lettuce, potato, strawberry, tomato	Bean, pea, cucumber, dill, tomato, pumpkin, squash
Parsley	Roses, asparagus	...
Pea	Carrot, corn, cucumber, Aubergine, lettuce, radish, spinach, tomato, turnip	Onions, garlic, shallots
Pepper	Basil, carrot, lovage, marjoram, onion, oregano	Fennel, kohlrabi
Potato	Broad bean, Cabbage, cauliflower, corn, lettuce, onions, peas, petunia, marigold, radish	Apple, pumpkin, tomato, sunflowers
Pumpkin	Bean, corn, mint, nasturtium, radish, marjoram	Potato
Radish	Bean, Cabbage, cauliflower, cucumber, lettuce, melon, parsley, tomato	Grape, hyssop, squash,
Ragweed	...	Reduces flea beetles
Rosemary	...	Deters bean beetles, white Cabbage moths, carrot flies, and many other insects
Rue	...	Deters beetles and fleas
Sage	...	Deters Cabbage worms, Cabbage white butterfly, and root maggots
Southernwood	...	Deters Cabbage white butterfly, carrot flies, aphid
Spinach	Cabbage, celery, Aubergine, onion, pea, strawberry, fruit trees	...
Squash	Bean, corn, mint, nasturtium, radish	...
Summer Squash	Bean, corn, mint, nasturtium, radish	Potato
Tansy	...	Deters many insects including ants, aphids, and Cabbageworms. Planted in a ring around fruit trees, helps repel fruit fly
Thyme	...	Deters Cabbage worms, whiteflies
Tomato	Asparagus, basil, beans, Cabbage, onion, parsley, pea, sage	Carrot, cauliflower, chives, fennel, potato
Turnip	Pea	...
Wormwood	General insecticide;	Deters mice and other rodents, slugs & snails. Repels carrot fly
Zucchini	Bean, corn, marjoram, mint, nasturtium, radish	Potato

Plants to attract insects

Most blue coloured flowers will attract bees, some more than others, depending on the shade of blue. Red and yellow flowers tend to attract beneficial insects such as hoverflies. Some, but not all white flowers attract bees.

Basil	Attracts bees
Buddleia	Attracts bees
Lemon Balm	Attracts bees and helps pollination

The insects that you need to attract

Birds

Although they are regarded as a pest in the productive garden, birds in fact do more good than harm. They eat numerous grubs, caterpillars, slugs and aphids, and can be encouraged into the garden by incorporating bird baths, food tables and nest boxes in you garden. Nesting requirements for different birds vary; you can obtain all the necessary information from the R.S.P.B.

Ground Beetles

Black ground beetles feed on eelworms, cutworms, leatherjackets and other insect larvae and eggs. You can encourage them by keeping the ground covered, so that they have a leaf litter to hide under during the day. At night they will come out to feed on the pests.

Centipedes

Centipedes are fast moving predators of small insects and slugs. They need ground cover to under during the day. At night they will emerge to find prey and even climb the plants to find it.

Frogs and Toads

You should definitely try and encourage frogs and toads into your garden, as they are an excellent means of slug control. They also eat woodlice and other small insects. A garden pond is the ideal environment for them, but they only need water for breeding purposes.

Hedgehogs

A family of hedgehogs is a great boon to any garden. They will eat slugs, cutworms, woodlice, millipedes and wireworms. It is difficult to attract them to your garden but try to encourage them by keeping a pile of logs in one corner of the garden and by leaving out saucers of cat/dog food and water.

Hoverflies

It is the larvae of these creatures that resemble thin wasps that devour great numbers of aphids. They can be encouraged into your garden by planting Tagetes, Calendula and Nasturtiums.

Lacewings

Again it is the larvae that eat aphids. Although they lay their eggs on the underside of plants, they do not cause any harm. (See How to Make a Lacewing House)

Ladybirds

Both the easily recognised adult and the less recognised grey larvae eat vast quantities of aphids. They can be encouraged by growing a varied selection of plants.